Vehicle-to-Vehicle (V2V) and Vehicle-to-Everything (V2X) technologies have been standardized by the 3rd Generation Partnership Project (3GPP) in Release 14 (Rel-14). V2V/V2X services are supported on the sidelink and reuse much of the Device-to-Device (D2D) work already standardized in Rel-12 and Rel-13. The term “sidelink” refers to communication performed between one user equipment (UE) and one or more other UEs without data being transmitted through an Evolved Node B (eNB) or other centralized controller. In particular, V2V/V2X messages are broadcast by a source without a priori knowledge of a receiver.
In Rel-15, the V2V/V2X work is expected to continue for both Long Term Evolution (LTE) and New Radio (NR) Scalable Network. In particular, it is likely that more advanced vehicular services such as platooning, automated merging, and a general move towards autonomous cars will be standardized. The work has already started in the 3GPP Service and System Aspects Group 1 (SA1), where requirements for V2V/V2X services are being drafted.
One of the requirements for advanced V2V/V2X services is the need for higher transmission reliability, for both multicast and unicast transmission. With transmission mode-4 (UE being autonomous without eNB allocating resources), the Rel-14 V2V/V2X solution might not provide adequate reliability. Thus, there is a need for techniques for improved mode-4 reliability.